2, 6-di-tertiary-butyl-4-methyl phenol



Pa tented 9 1941 zfi nl-TEkTlARY-BUTYL-d-Mlmli I PHENOL Donald R. Stevens, Swissval'e, and William A.

Gruse, Wilkinsburg, Pa., assignorl to Gulf Oil Corporation, Pittslmrgh, Pa., a corporation of Pennsylvania No Drawing. Original application April 12, 1937, Serial No. 136,504. Divided and this application January 16, 1939, Serial No. 251,280

7 1 Claim. This invention relates to tri-alkylated monohydroxy phenols, and more particularly to 2,6-ditertiary-butyl-4-methyl-phenol, a compound which is soluble in oil and insoluble in water and in dilute aqueous alkali so1ution,--and which possesses the property of inhibiting oxidational changes in petroleum hydrocarbon products when added thereto in relatively small amounts; all as more fully hereinafter set forth and as claimed.

This application is a division of our copending application for United States Letters Patent obtained by treating low boiling cracked distillates, such as cracked gasoline containing olefins such as propylene and butylene, with aryl-hy- -droxy compounds such as phenol, cresols or xylenols at a relatively low temperature in the presence of an acid condensing agent, or at a relatively high temperature in the absence of an acid condensing agent. In our copending application Serial No. 110,014, filed November 9, 1936, which is a division of application Serial No. 702,258, we have described and claimed antioxidant materials as thus produced and hydrocarbon products containing them.

After considerable research we succeeded in identifying the chemical character of certain of the constituents of the antioxidant materials described and claimed in our aforesaid applications and in our copending application Serial No. 136,504, filed April 12, 1937, which is a continuation-in-part of the previously filed applications referred to hereinabove, we have described and claimed for use as antioxidants, particularly in petroleum oils, a class of compounds consisting of the 2,4,6-tri-a1kylated monohydroxy phenols having in a position ortho to the hydroxy group at least one alkyl substitution group having three or more carbon atoms, e. g., a propyl, butyl, amyl, or high alkyl group, the remaining alkyl groups being similar or different for example methyl, ethyl or higher alkyl groups, which, compounds are soluble in oil and insoluble in dilute aqueous alkali solution and in water. The present application is concerned with one of this newly discovered class, disclosed in said application Serial No. 136,504, namely, 2,6-di-tertiary-butyl-4- methyl-phenol which we have synthesized in substantially pure form.

We have discovered that by alkylating paracresol or para-methyl-phenol with isobutylene until no more isobutylene reacts with the paracresol, we can produce 2,6-di-tertiary-butyl-4- methyl-phenol, a compound which is soluble in oil and insoluble in dilute aqueous alkali solution. We have discovered also that this compound possesses good antioxidant properties and when added to petroleum oil products such as gasoline, lubricating oils, transformer-mils, turbine oils and the like, in relatively small amounts it stabilizes these materials against oxidational changes.

In preparing 2,6-di-tertiary-butyl-4-methylphenol, isobutylene, either alone or in admixture with other hydrocarbons, may be used in alkylating the para-cresol. Cracked gasoline as normally produced, and the heavier of the hydrocarbons usually found as vapors in cracking-still gases contain varying quantities of isobutylene as well as higher olefins, and may be used as starting materials. 011 the other hand, the isobutylene may be used in isolated form or in admixture with other closely related olefins or paraflins. For example so-called debutanizer gas may be employed as a starting material, as may isobutylene itself. It will be readily understood that when it is desired to prepare 2,6-di-tertiary-butyl- 4-methyl-phenol, free or substantially free from other compounds, the raw material should not comprise mixtures of olefins or mixtures ofcresols, except in those cases in which the natures of the individual products will permit easy isolation and separation after alkylation. As to mixtures of isobutylene and parafiins such as butane,

the presence of the paraflin has no effect on the operation other than to reduce the concentration of the isobutylene; the butane does not enter into the reaction with the para-cresol.

In general the methods set forth in our prior applications referred to hereinbefore may be employed in preparation of 2,6-di-tertiary-butyl-4- methyl-phenol, with due regard to the selection of the raw materials. Thus at temperatures up to F. or thereabouts, and under atmospheric or moderately elevated pressures, the usual conv2 densing'agents are employed, including sulfuric acid, phosphoric acid. anhydrous aluminumf cause decomposition of the para-cresol.

chloride, boron tri-fluoride, ferric, chloride. hydrogen chloride and the like. Sulfuric acid is ordinarily most satisfactory by reason of its efliciency and cheapness. The amount of acid condensing agent, required is relatively small with respectto the amount of para-cresol; in some instances the amount of acid condensing agent required is as little as 1 per cent of the paracresol orles's, being in such instances present in catalytic amounts. In using sulfuric acid as the condensing agent, and when it is desired; to

utilize the isobutylene efllciently, it is usually better to employ the acid in an amount equal to not less than about 3.0 per cent of the paracresol. More than per cent of the condensing agent, based on amount of para-cresol, is not and pressures so high that the product obtained will predominate in polymerized isobutylene, the formation of which is enhanced by heat and pressure.

The reaction involves no special difficulties, the reacting ingredients being simply contacted in the usual manner either continuously or in batch operation. After completion of the reaction the products are usually washed with an aqueous solution of caustic soda orother equivalent alkali, the strength of the washing solution being preferably not over per cent. This washing operation removesany remaining acid condensing agent and also removes all alkali soluble mate'- rial such as any unreacted para-cresol, as wellas alkylation products in which the alkylation has not'proceeded to the point desired. Water washing may also be resorted to wherever desired. The washed product may then be distilled under ordinary pressure or under vacuum and recrystallized in the usual manner to separate the byproducts and obtain substantially pure 2,6-ditertiary-butyl-i-methyl-phenol.

In,g eneral we find it advantageous to employ ordinary concentrated sulfuric acid in amounts corresponding to aboutfrom 3 to 5 per cent by v weight of the para-cresol; with this concentra tion the rate of condensation is sufiiciently high while with higher amounts of acid the tendency toward polymerization of. the isobutylene is increased. We also find it advantageous in obtaining a major proportion of 2,6-di-tertiarybutyl-i-methyl-phenol in the total products of the reaction to maintain the reaction. temperature at a relatively low temperature during the first period of condensation until the condensation products form a magma or mush, after which we find it desirable to raise the temperature enough to maintain the reaction mass in a.

more or less liquid condition, thereby facilitatin contact between the reacting materials. 1' For example 500 parts by weight of para-ores of a technical grade and25 parts by weight of commercial concentrated sulfuric acid were introduced into a suitable reaction vessel provided with'a gas inlet and a gas outlet, suitable agitating means and a coil for heating or cooling the contents of the reaction vessel. Isobutylene was then. bubbled through the para-cresol, which was maintained at a temperature of 70 C. with agitation. After the reaction had been substantially completed, as indicated by the fact that the reaction mixture no longer gained in volume,

as well as by the flow of isobutylene at the gas exit, the flow of gas was stopped and thereaction mixturewas blown with steam and washed with hot water and weak alkali solution until neutral. There was obtained a yield of 87 per cent of an oil which upon cooling solidified to a light gray crystalline. mass. Recrystallization 1 from hot absolute alcohol gave white crystals having a melting point of approximately 69.0 C. and havingan ultimate analysis corresponding extremely closely to the theoretical ultimate analysiscalculated 'for 2,6-di-tertlary-butyl-4- methyl-phenol.

The compound prepared as indicated hereinabove, when added to a standard reference gasoline having an oxygen stability period oi 1 hours, in an amount equal to 0.04 gram per 100 cc. of the gasoline, increased the induction period to 10 hours, indicating an extremely satisfactory antioxidant effect, especially when viewed in the light of the cheapness and ease of preparation of the antioxidant, and in view of the fact that this compound is insoluble in water and in dilute caustic alkali solution.

This compound was tested as an antioxidant for turbine oil with extremely satisfactory results. The turbine oil employed in testing was an oil which has heretofore been considered as a commercially satisfactory product for the lubrication of steam turbines, although subject, as are other oils, to oxldational deterioration, and hence open to improvement in that respect. It was a paraflln base oil which had been highly reflned to give the following characteristics;

Viscosity in seconds S. U. V.

At F- 150 At F 85 At 210 F 43 Gravity A. P. I -1 32.5 Flash (Cleveland open cup method) 390 Fire test F.. 460 Pour point F 0 Color N. P. A 1 Carbon residue trace We determined the tendency of this turbine oil to oxidize in use and compared this with the tendency toward oxidation of the same oil having incorporated therein a small amount of 2,6-ditertiary-butyl-4-methyl-phenol, thus forming a more stable composition in accordance with our invention. The tendency toward oxidation was determined in both cases by a standardized method of testing steam turbine oils, being that of Rogers 8: Miller, (Ind. Eng., Chem. 19, 308, 1927), modified in that we controlled the supply of oxygen by metering to provide 5 liters per hour;

. we used a 400'gram sample instead of a 500 gram sample, and ran the test in the presence of 25 cc. of distilled water and in the presence of metallic iron and copper. The presence of water necessitated the provision of a reflux condenser to prevent loss from volatilization. About'3 feet each of fine iron wire and fine copper wire were submerged in the oil during the test.

In this test the deterioration of the oil, due to oxidation in'the presence of water, iron and copper, is measured in terms of neutralization numbers and steam emulsion numbers over a long period of time while the oil undergoing test is subjected to conditions of accelerated oxidation.

The following table indicates the relatively high stability of our composition as compared to the uninhibited oil:

Uninhz'bited turbine oil Time of test in hours Same turbine oil containing 0.2% 2,6-di-tertiarybutyZ-4-methyl-phenol Time of test in hours Neutralization No Steam emulsion No The same compound was round to be an excellent antioxidant for transformer oil.

While the methods set forth in our previously filed applications are generally applicable for the preparation of 2,6 (ii-tertiary butyl-4-methylphenol, other methods of synthesizing this compound will readily suggest themselves to those skilled in the art and may be used when desired.

While we have described our invention hereinabove with respect to various specific illustrative examples, it will be obvious that our invention is not limited to the details of such examples, but may be variously practiced and embodied within the scope of the claims hereinafter made. It will also be understood that our invention is not limited to the use, as antioxidants, of isolated compounds of the class described, but contemplates also the use of these compounds in admixture with other compounds of the same class, as well as other materials of an entirely different character, wherever this proves desirable.

What we claim is:

2,6-di-tertiary-buty1-4-methyl-pheno1.

DONALD R). STEVENS. WILLIAM A. GRUSE. 

